The Salt River Basin in northeastern Missouri is the source of water to
the Mark Twain Lake, an 18,600-acre Army Corp of Engineers reservoir that
is the major public water supplier in the region. The Salt River system
encompasses an area of 2,518 mi2 within portions of 12 northeastern Missouri
counties. Sub-watershed areas monitored will range from 28 mi2 to 460 mi2.
Soils within the basin were formed in Wisconsin and Illinoian loess overlying
pre-Illinoian glacial till. Illuviation of the high clay content loess
resulted in the formation of argillic horizons containing 40-60% smectitic
clays. Topography within the watershed is flat to gently rolling, with
most areas having 0-3% slopes. The Adco-Putnam-Mexico soil association
predominates in the flatter upland areas, and these soils tend to be less
eroded and have greater depths to the claypan than the terrace areas. The
Mexico-Leonard soil associations occur in more sloping terrace and alluvial
areas where the depth to claypan is often <15 cm on side slopes because
of erosion. The claypan is not present within alluvial areas immediately
adjacent to streams. The naturally formed claypan represents the key hydrologic
feature of the basin, and it is the direct cause of the high runoff potential
of these soils. Most soils within the basin are classified as Hydrologic
Group C or D by NRCS. Land use is predominately agricultural within the
basin. The primary row-crops are soybeans, corn, and sorghum. Forage production
is mainly tall fescue. Livestock production is mainly beef cattle, but
swine operations are increasing, particularly in the Middle and Elk Fork
watersheds. Average annual precipitation is about 1000 mm per year, and
stream flow (based on Goodwater Creek data) accounts for about 30% of precipitation.
Runoff accounts for about 85% of total stream flow. Despite high runoff
potential and poorly drained soils, sub-surface drainage is not employed
because of the difficulties of installation in or below the claypan.

The basin has a known and well-documented history of herbicide and sediment
contamination problems. The naturally formed claypan soils that predominate
within the basin create a barrier to percolation and promote surface runoff.
This results in a high degree of vulnerability to surface transport of
sediment, herbicides, and nutrients. Mark Twain Lake serves a public drinking
water supply for approximately 42,000 people, and consistently high spring
and summer time atrazine levels have been an on-going concern. More recently,
late summer algal blooms have created the need for more extensive water
treatment to reduce odor and taste problems in drinking water, and may
be a reflection of increased nutrient transport within the basin. Water-borne
pathogen contamination of the major sub-watersheds of the Salt River basin
has not been extensively studied to date. It is anticipated that this may
be a problem in those subwatersheds with significant animal feed operations.

Studies are currently underway at field and plot scales to study the water
quality impact of several different conservation practices. These studies
include: Implementation of a precision agricultural system on an 88-acre
field (590, 329A),Plot-scale studies of the effectiveness of grass filters and grass hedges
on contaminant mitigation from edge-of field runoff and parallel tile outlet
discharge (393),alternative weed management systems focused on reducing herbicide inputs
(595),measuring soil quality under different cropping systems, and the potential
for enhanced herbicide degradation in contour grass buffer strips (332). In addition, hydrologic simulation models will be used to predict water
quality at multiple scales, determine contaminant source areas within watersheds,
and serve as decision support aids for BMP implementation.

Prevailing and traditional agronomic practices for row crop production
have degraded soil and water resources in the Midwestern claypan soils
region. Soil and water quality are inextricably connected, and surface
runoff is the key hydrologic process that physically links them. Individual
research projects are integrated by the development, implementation, and
assessment of Best Management Practices (BMPs) to improve soil and water
quality. An additional level of impact stems from the development of watershed
models as tools for BMP assessment and watershed planning.

The implementation of Best Management Practices (BMPs) to improve soil
and water quality must be balanced with the need for socially acceptable
practices that sustain profitable crop production. Our vision to meet this
challenge entails an array of conservation, agronomic, and soil management
practices. The proposed research encompasses three main approaches:

(1) studies addressing the parameters and practices that control soil
and water quality; (2) studies designed to test the effectiveness and economic impact of
various BMPs and alternative weed management strategies;and (3) application of computer models to simulate the impact of BMPs
on surface water quality at field and watershed scales.

These broad objectives are divided into nine individual projects tied
together by a common goal: the effective implementation of BMPs to improve
and sustain soil and water resources. Projects include studies ranging
from assessment of soil and water quality to application of genetic-based
techniques for detection of water-borne pathogens to development and testing
of new agronomic and conservation management practices. Expected results
include improved indexing of soil quality parameters, new and profitable
BMPs for field crop production that protect or improve soil and water quality,
and a validated model for improved surface water quality assessment and
planning.

Measurements In Place and Planned Water quality monitoring at Goodwater
Creek and at an 88-acre farm field within Goodwater Creek watershed will
continue during CEAP. The field and watershed monitoring stations are equipped
with v-notch weirs and automatic samplers. The automatic samplers are equipped
with pressure transducers to measure the height of the water column for
computing stream discharge. At the field scale, samples are collected for
all runoff events. Shallow groundwater is also collected at two locations
within the field twice each year and analyzed for dissolved nitrate levels.

At the watershed scale, grab samples are collected weekly, and all runoff
events are sampled by the automatic sampler. In addition, the USGS has
an extensive network of hydrologic monitoring stations at nearly all major
watersheds that discharge into Mark Twain Reservoir, as well as a monitoring
station at the reservoir outlet (Fig. B3). Thus, stream discharge into
and out of the reservoir is well characterized. In order to have a complete
water quality monitoring network for computing the mass balance of contaminants
into and out of the reservoir, additional monitoring stations will need
to be established at Black Creek and Otter Creek (Fig. B3).

In addition, two new monitoring sites will be established within the Long
Branch Creek watershed to provide a multi-scale assessment of water quality.
At all surface-monitoring sites, contaminant monitoring will include commonly
used corn and soybean herbicides, dissolved and total N and P, and sediment.
Newly established sites will have rating curves developed to compute discharge.
Enumeration of fecal coliforms and detection of pathogenic bacteria will
be conducted periodically to assess the extent of pathogen contamination
in the major sub-watersheds of the Salt River.